Just as you have a lens in your glasses to focus there is a lens in the eye to focus. When you are young this changes shape to bring things into focus. As you age it stops changing shape and reading glasses are subsequently required (presbyopia).
Problems occur when the lens loses its clarity and becomes opaque. This causes blurring that can not be corrected with glasses. This is known as a cataract. Cataract surgery is the commonest operation in the country.
Glasses (Refractive Error / Laser)
Cloudy Lens (Cataract)
Complicated Cataract (weak zonules, dislocated lens)
Blur After Cataract (Capsule Opacification, Laser)